Support Google Play 16 KB Page Size Requirement (#13470)

- See: https://developer.android.com/guide/practices/page-sizes#update-packaging
- Also, make min API uniform at 21 (from 16 and 23 in a few places)

android-project/app/build.gradle

@@ -19,7 +19,7 @@ android {
                 abiFilters 'arm64-v8a'
             }
             cmake {
-                arguments "-DANDROID_PLATFORM=android-21", "-DANDROID_STL=c++_static"
+                arguments "-DANDROID_PLATFORM=android-21", "-DANDROID_STL=c++_static", "-DAPP_SUPPORT_FLEXIBLE_PAGE_SIZES=true"
                 // abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
                 abiFilters 'arm64-v8a'
             }